This invention relates to apparatus for filtering particulate matter from a gaseous fluid and more particularly to improved apparatus for cleaning upstanding filter bags mounted longitudinally within a housing to collect particulate matter on the inner surface thereof while permitting clean gas to pass therethrough.
Heretofore in the art to which our invention relates, particulate matter entrained in a gaseous fluid has usually been collected on filter bags by two different methods. In one method the particulate matter is collected on the outer surface of the bag while in the other method the particulate matter is collected on its inner surface. An elongated wire cage is required with the first method to prevent the bag from collapsing when the gaseous fluid engages the outer surface of the filter bag. With both methods, each filter bag must be properly tensioned to provide a maximum filtering surface and to compensate for any variation in length of the bag created by temperature and humidity changes within the bag house.
Heretofore, it has been the usual practice to employ conventional mechanical or pneumatic devices to clean the filter bags. Such mechanical devices usually employ shaking, vibrating or oscillating mechanisms to jar collected particulate matter loose from the filter bags. An electric motor is usually operatively connected to wear-proned cams and other linkage members to produce the shaking, vibrating or oscillating motion. Mechanical devices of this type require considerable time, labor and maintenance to assure proper operation thereof. Also, deterioration and wear of filter bags has been experienced with such mechanical shakers and vibrators due to the fact that the bags rub against their supporting cages during the cleaning cycle.
While pneumatic devices may eliminate the usage of wear-proned cams and other linkage members, such devices require the use of expensive pumps, motors, valves and pneumatic lines. Also, to clean filter bags with a pneumatic device, the flow of the gaseous fluid carrying the entrained particulate matter must always be shut off in the compartment of the bag house being cleaned. Air or gas is then introduced to bring about a reverse pulsation of air within this compartment to vibrate and shake the bags. Most bag houses with which we are familiar have been used to clean a gaseous fluid containing considerable amounts of carbon particles and very little oxygen. Accordingly, the introduction of reverse air or gas flow into the compartment being cleaned combined with the carbon particles collected on the filter bags may create a highly flamable mixture under certain conditions. That is, with an excessive temperature rise or a spark within the compartment being cleaned, the mixture could ignite and burn the filter bags. This is the major cause for the phenomenon known in the art as "bag house burn-out".
Conventional mechanical and pneumatic cleaning devices with which we are familiar are disclosed in the following U.S. patents: No. 2,137,254; No. 3,008,543; No. 3,377,781; No. 3,939,971; No. 4,113,455; and No. 4,157,901.